rectangularity_xld — Shape factor for the rectangularity of contours or polygons.
rectangularity_xld calculates the rectangularity of
each input contour or polygon in
XLD. The input contour or polygon
must not intersect itself, otherwise the resulting parameter is not
meaningful (Whether the input contour or polygon intersects itself or not
can be determined with
the input contour or polygon is not closed it will be closed automatically.
To determine the rectangularity, first a rectangle is computed that has the same first and second order moments as the input contour or polygon. The computation of the rectangularity measure is finally based on the area of the difference between the computed rectangle and the input contour or polygon normalized with respect to the area of the rectangle.
rectangularity_xld returns the value 1. The more the
input contour or polygon deviates from a perfect rectangle, the less the
returned value for
Rectangularity will be. If more than one contour
or polygon is passed, the results are stored in tuples in the same order as
the respective contours or polygons in
For input contours or polygons which orientation cannot be computed by using
second order moments (as it is the case for squares, for example), the
Rectangularity is underestimated by up to 10% depending
on the orientation of the input contour or polygon.
Contours or polygons to be examined.
Rectangularity of the input contours or polygons.
0 <= Rectangularity && Rectangularity <= 1.0
rectangularity_xld returns the value 2 (H_MSG_TRUE)
if the input is not empty.
The behavior in case of empty input (no input contours or polygons available)
is set via the operator
If necessary an exception is raised.
P. L. Rosin: “Measuring rectangularity”; Machine Vision and Applications; vol. 11; pp. 191-196; Springer-Verlag, 1999.